Electrical relay containing a pyrotechnical charge and having no moving parts

ABSTRACT

A static relay comprising a box containing two spaced metallic electrodes which are electrically isolated from one another. A first pyrotechnical composition is disposed between the electrodes and a second pyrotechnical composition is contained in the box separate from the first pyrotechnical composition. An energizing filament is in contact with the second pyrotechnical composition to effect initiation thereof upon application of an electrical signal to the filament. The first composition is so disposed in the box with respect to the second composition as to be initiated by the reaction thereof, the first composition being constituted of a pulverulent mixture of a metal oxide and a metalloid reducer so as to form a molten conductive body of the reduced metal under the heat released by the reaction of the first composition, which molten body effects welding of the metallic electrodes together. In one embodiment, the first pyrotechnical composition serves by itself as an insulator between the electrodes and in a second embodiment a ring is interposed between the electrodes to form with one electrode a chamber in which the first pyrotechnical composition is confined and a thin layer of air with the second electrode.

United States Patent Delgendre et al.

1 ELECTRICAL RELAY CONTAINING A PYROTECIINICAL CHARGE AND HAVING NO MOVING PARTS Inventors: Jacques C. Delgendre, Toulon;

Emile F. Hamon, La Seyne-sur-Mer; Georges A. Berton, Toulon, all of France [73] Assignee: Etat Francais, Paris, France [22] Filed: Mar. 18, 1974 [21] Appl. No.: 452,373

[451 Sept. 30, 1975 Primary Examiner-Robert K. Schaefer Assistant E.\'aminer--John W, Redman Attorney, Agent, or Firm-Waters, Schwartz & Nissen [5 7 ABSTRACT A static relay comprising a box containing two spaced metallic electrodes which are electrically isolated from one another. A first pyrotechnical composition is disposed between the electrodes and a second pyrotechnical composition is contained in the box separate from the first pyrotechnical composition. An energizing filament is in contact with the second pyrotechnical composition to effect initiation thereof upon application of an electrical signal to the filament. The first composition is so disposed in the box with respect to the second composition as to be initiated by the reaction thereof, the first composition being constituted of a pulverulent mixture of a metal oxide and a metalloid reducer so as to form a molten conductive body of the reduced metal under the heat released by the reaction of the first composition, which molten body effects welding of the metallic electrodes together. In one embodiment, the first pyrotechnical composition serves by itself as an insulator between the electrodes and in a second embodiment a ring is interposed between the electrodes to form with one electrode a chamber in which the first pyrotechnical composition is confined and a thin layer of air with the second electrode.

26 Claims, 11 Drawing Figures Ill- US. Patent Sept. 30,1975 Sheet 1 0f 5 3,909,567

U.S. Patent Sept. 30,1975 Sheet 2 of5 3,909,567

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FIG. 5

1212' H I i 38 5370. 3% X A l 39 III E hi U.S. Patent Sept. 30,1975 Sheet 3 of 5 3,909,567

F1627 A f )I II ELECTRICAL RELAY CONTAINING A PYROTECI'INICAL CHARGE AND HAVING NO MOVING PARTS FIELD OF THE INVENTION The invention relates to electrical relays containing a pyrotechnical composition, the instantaneous combustion of which serves to make the relay conductive. The relay has no moving parts and as such will be designated a static relay.

More particularly, the present invention is directed to static electric relays in which an element establishing the electrical closing of a circuit is a conductive body produced by the reaction of a first pyrotechnical composition placed in the space separating two electrodes connected in the circuit, said reaction being produced by the combustion of a second pyrotechnical composition which is electrically energized.

The technical field to which the invention is directed is the construction'of static electrical relays which perate irreversibly including miniaturized relays applicable for use in missiles, torpedoes, engines and mines as well as in control circuits, logic circuits and memory banks.

BACKGROUND There are already known, interrupters or relays comprising two conductors electrically connected to one another by a conductive mixture, which mixture upon burning, produces a nonconductive body which causes openingof a circuit.

It is also known to produce static, electrical relays adapted to open or close an electrical circuit through the intermediary of an insulative or conductive body produced by the reaction of a pyrotechnical composition.

French Pat. No. 71-18979 describes static electric relays adapted to establish the opening or closing of an electric circuit through the intermediary of an insulative or conductive body produced by the reaction of a pyrotechnical composition under the effect of heat released by the combustion of a second pyrotechnical composition which is electrically activated.

By the term pyrotechnical composition is meant at least two substances which react with one another in exothermic fashion such that the reaction, initiated by an energy pulse, continues substantially instantaneously.

SUMMARY OF THE INVENTION An object of the invention is to provide improvements in relays of the above type which are adapted to control the closing of a circuit.

The objective of the invention is achieved by a relay by which the closure of an electrical circuit is effected in irreversible manner whatever the conditions of temperature, pressure, or field of force in which the relay is placed, said relay before the reaction providing very good insulation between the two electrodes in the circuit, and after the reaction providing very good conductivity between the electrodes.

The relay comprises a first insulative pyrotechnical composition separating-two electrodes connected in an electrical circuit, the closing of the circuit being effected by a conductive body produced by the reaction of this first pyrotechnical substance, said reaction being effected by the combustion of a second pyrotechnical composition which is electrically activated.

The relay according to the invention comprises two metallic electrodes, the heat released by the reaction of the first pyrotechnical composition causing electrical connection of the two electrodes through the intermediary of the conductive body produced by the reaction of said pyrotechnical composition.

In order to facilitate the electrical connection of the electrodes, the first pyrotechnical composition comprises a pulverulent mixture of a metal oxide and a reducing agent such that upon reduction of the oxide, the metal is freed which serves as a metal support to effect welding of the electrodes together.

Metal oxides are generally very good electrical insulators. In contrast, the insulative properties of most reducing agents capable of reducing metal oxides, are not as good.

According to the invention, the reducing agent is a metalloid of low atomic weight having high resistivity, such as, boron or silicon.

The metalloid of low atomic weight is present in the mixture of two components in stoichiometric amount and hence the proportion of reducing agents, which is less insulative, is less than 20%, which will not substantially alter the insulative properties of the mixture.

For the same purpose, there is utilized an oxide of a heavy metal which is a good conductor and is relatively low in oxygen content and easy to reduce. According to the invention, there is used an oxide of a metal having a normal potential of oxygen reduction greater than 0. 15 volts, positive or very slightly negative. Preferably, there is used an oxide of a metal selected from the group of tin, lead, copper and silver.

In the pulverulent state, the mixture of metallic oxide and of reducing agent, such as boron or silicon has a high resistivity.

Another object of the invention is to provide miniature relays having a size of the order of a centimeter or less and capable of use on the same supports as static semi-conductor relays, so that they can be interchangeable with such relays.

To attain this objective, it is necessary to dispose these electrodes very close to one another with a spacing of the order of a millimeter and to compress the first pyrotechnical composition to increase the density of the mixture and provide, between the electrodes, a sufficient quantity to effect the welding of the two electrodes. Nevertheless, the resistivity of the compressed mixture must still be sufficiently high to assure the electrical insulation between the electrode prior to combustion.

To eliminate any risk that the electrical isolation between the electrodes will become insufficient, there is added to the mixture, before the compression thereof, a silicone liquid insulator such as oil of methyl silicone of the general formula This oil also serves as a hydrophobic agent. At the time of combustion of the pyrotechnical composition, the oil utilized in small quantities decomposes and yields a small solid residue and the release of a very small amount of gas.

Additionally, in order to add to the rigidity of the dielectric between the electrodes, there is applied to the electrodes a coating of an insulating varnich which is combustible at moderate temperature without leaving a solid residue, as for example a coating of nitrocellulose.

The electrodes of the relay according to the invention can be constituted of a metal having a certain af finity for the product of the reaction of the first pyrotechnical composition or it can have a coating of a metal having a very low melting point such as tin.

According to a characteristic of the invention, the electrodes have the form of parallel plates separated by a small spacing filled with the first pyrotechnical composition. For example, the electrodes can be formed as two coaxial cylindrical plates.

This arrangement has a number of advantages.

The section for current flow after welding of the electrodes is very high to provide an especially low electrical resistance.

The transverse section of the weld or junction between the electrodes is increased to provide a better mechanical resistance to the junction, from which there is obtained better resistance to mechanical and thermal forces.

The electrodes in plate form serve at the same time as the lateral walls of a receptacle containing the pulverulent mixture and lightly compressing the same such that it will remain between the plates.

The result of the invention is a new product constituted by a pyrotechnical static relay.

The advantages of the relay are the following:

It is entirely static, without any moving parts whatsoever, yet having great operational capability. The time of the control impulses is less than one millisecond.

Once the circuit is closed by welding of the two electrodes together, the closure is irreversible which enables the relay to resist the conditions of the ambient en vironment, i.e. high temperature or electromagnetic or radioactive radiation.

A particular application, but not exclusive of the relay according to the invention, is in the circuits for remote guidance or remote control of engines such as in missiles, torpedoes, rockets and the like for permitting these to resist severe environmental conditions either natural or produced by the defensive action of an adversary.

The relays according to the invention can be miniaturized and in the form of conventional electronic components such as transistors or integrated circuits. They can also include pin connections for attachment in integrated circuits of dual type in-line.

The energy necessary to control the closure of the circuit can be furnished by electrical signals of extremely short duration which permits placement of a large number of relays according to the invention on an engine having a voltage source of low power. Notably, the relays can be mounted in combination to constitute logical circuits.

There can be interposed between the first and the second pyrotechnical charges, an intermediate charge to obtain a predetermined delay between the firing signal and the closing of the circuit.

According to a further aspect of the invention it is sought to increase the insulative property of the first pyrotechnical charge without changing the composition and without adverse effect on the closure of the circuit between the electrodes.

The first pyrotechnical composition which is initially insulative has a relatively low breakdown voltage which changes under permanent electrical voltage. It has been sought to remedy this by adding silicones to the first pyrotechnical composition. The release of gas at the time of combustion could cause poor operation of the relay. Another solution is the application of insulating varnish on the electrodes. This varnish is, however, too fragile to resist the phase Change.

The invention according to said further aspect seeks to provide isolation of the two electrodes while permitting obtention of a breakdown voltage which is suffi ciently high, without changing the first pyrotechnical composition, nor deteriorating the closure of the circuit between the two electrodes.

The invention according to this further aspect is characterized in that said interval between the electrodes comprises in addition to the first composition, a layer of air which disappears under the effect of the combustion of the first composition. This volume of air constitutes a sort of detent chamber limiting the internal pressure which is able to be created at the time of the reactions of the pyrotechnical compositions.

The relay additionally comprises an envelope which defines with one of the electrodes, a chamber containing the first composition and separated from the other electrodes by said layer of air. This arrangement permits the removal of the first composition from the effect of all permanent electrical voltage while providing a relatively high breakdown voltage, all without requiring the insulative property otherwise required for the first composition before the reaction.

This envelope is in one embodiment made of a combustible material, no longer offering after the reaction, any obstacle to the conduction in the interval separating the electrodes.

In an embodiment where the two electrodes are cylindrical and coaxial, the envelope is a coaxial ring with bent edges defining a closed space with one of the electrodes.

A variant provides for welding of the two electrodes, under the effect of the heat released by the combustion of the second composition, by means of said envelope which is made of a fusible conductive metal which joins with the free metal of the first composition to weld said electrodes. This disposition enhances the closure of the circuit between the electrodes after welding, while assuring high resistence to mechanical forces or temperature.

Furthermore, in the actuator circuit, which comprises a filament whose ends are connected to the extremities of two conductors for initiating the second pyrotechnical composition, said extremities at which the filament is connected being coated by an insulator resistant to the heat released at the time of the combustion of the second composition. This permits avoiding the inconvenience often encountered when utilizing the known relays. Namely, since the residues of the second pyrotechnical composition are more or less conductive, it happens after the initiation that current continues to pass between the two conductors nevertheless insulated.

A membrane is additionally applied against the sec ond pyrotechnical composition at its face opposite to that in contact with said filament, maintaining said second composition against said filament and defining with the internal electrode, and the cover a volume of air which constitutes a detent chamber, limiting the internal pressure which can be produced at the time of the reactions of the pyrotechnical compositions.

The following description refers to the annexed drawings which represent, by way of example and without limitation, several embodiments of pyrotechnical relays according to the invention.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a transverse sectional view of a first embodiment of a relay according to the invention,

FIG. 2 is a sectional view taken along line IIII in FIG. 1,

FIG. 3 is a transverse sectional view of a second embodiment of a relay adaptable for use in circuits of high power,

FIG. 4 is a sectional view on enlarged scale of an arrangement for energizing the relay of FIG. 3,

FIG. 5 is a sectional view taken on line VV in FIG. 7 of a multiple relay arrangement including four relays in a common housing with connections identical to those of flat boxes of an integrated circuit,

FIG. 6 is a sectional view taken on line VI-VI in FIG. 5,

FIG. 7 is a sectional view taken on line VII-VII in FIG. 5,

FIG. 8 is a transverse section of a relay according to a further embodiment of the invention,

FIG. 9 is a transverse section of a relay according to another embodiment of the invention,

FIG. 10 is a perspective view of the embodiment of FIG. 9 broken away and cut in vertical and horizontal sections, to reveal interior details, and

FIG. 1 1 is a transverse section of a relay according to another embodiment of the invention.

DETAILED DESCRIPTION Referring to FIGS. 1 and 2 therein is seen a static relay composed of a box 1 of relatively small height, i.e. less than 1 cm. and closed in sealed manner by a cover 2. The box and cover are made, for example, of nickel and are assembled by welding or soldering.

At the interior of the box are disposed two cylindrical metallic electrodes 30, 3b which are concentric and separated by a small space of the order of 1 mm. A first pyrotechnical position 4 fills this space, this composition being, for example, a pulverulent mixture of silver oxide and boron. Such mixture is an electrical insulator and it is moderately compressed between the electrodes.

The quantity of boron in the mixture is substantially stoichiometric and since boron has a relatively low atomic weight, the weight proportion of boron is relatively low. Although boron has a lower resistivity than silver oxide, the electrical resistance of the mixture is nevertheless high, of the order of several megohms.

As a variant, the mixture 4 can be more strongly compressed and still be highly insulative by adding a silicone liquid thereto, for example, oil of methylsilicone of the general formula 3):; SiO 3)2 ln 3)a- The silicone not only increases the electrical resistance of the mixture permitting it to be compressed more strongly, but it also acts as a hydrophobic agent.

Each of the electrodes is welded to a conductor 5a, 5b, said conductors projecting from the exterior of the box to form connection terminals.

The electrodes 3a, 3b are electrically insulated from the box 1 by an insulating material 6 formed in two parts 6a, 6b and mating along plane 6c.

The lower part 6a has a circular groove 7 in which the electrodes 3a and 3b are placed. After having placed the pyrotechnical composition between the electrodes, the assembly is covered by the upper part 6b. A cavity 8 is formed at the interior of the internal electrode 3b and into this cavity 8 extends two conductors 9a, 9b which project from the exterior of the box to form two connection terminals.

Between the conductors 9a, 9b is connected a filament 10 which is embedded in a second pyrotechnical composition 11 disposed in cavity 8.

The internal electrode 3b is provided with hole 12 which open into the cavity 8.

The illustrated relay has an exterior form similar to that of a conventional electronic element, such as a transistor, and it can be connected to printed circuits. The exterior diameter of the relay is of the order of 1 The relay operates as follows:

An electronic circuit whose closure is desired at a given instant is connected to the conductors 5a, 5b. The composition 4 being an insulator, the circuit is open.

A second electronic control circuit is connected to the conductors 9a and 9b. This circuit receives control signals which can be impulses of very short duration, of the order of 1 millisecond.

These impulses are sufficient to produce heating of filament l0 and initiation of the second pyrotechnical composition 1 1. This composition serves for the initiation of the reaction of the first pyrotechnical composition 4. The composition 11 can be constituted of any suitable pyrotechnical mixture known in the art provided that the heat of combustion is sufficient to initiate the reaction of the first composition and that the quantity of gas produced is not too great. The holes 12 facilitate the energization of the first composition. The combustion of the first composition causes reduction of the silver oxide which leaves silver in the molten state which effects welding of the two electrodes 3a and 3b together.

In order to facilitate this welding, the electrodes 3a and 3b can be covered by ametal conductor having a low melting point, for example, a layer of tin.

Thanks to this welding of the two electrodes by the metal conductor produced by the reduction of the oxide, there is obtained a closing of the circuit with a very low resistance of the order of less than one-tenth of an ohm. The circuit closure is irreversible and absolutely insensitive to the effects of temperature, pressure, electromagnetic fields and mechanical forces produced by shocks or vibrations.

The filament 10 is melted by the reaction of the second pyrotechnical composition 11 thereby opening the control circuit.

The described arrangement is constructed as a relay of the type which can be activated by a control signal of very low duration consonant with very low strength, the greatest part of the energy which is necessary being furnished by the pyrotechnical reactions.

FIG. 3 is a transverse section of another embodiment of a relay according to the invention adapted to control the closing of electrical circuits in which the current fiow is high, for example, of the order of at least 100 amperes.

This relay is composed of a cylindrical insulating box 13, for example, of plastic material closed by a threaded stopper 14 of the same material.

Two connection terminals 15a and 15b enable the relay to be connected in an electric circuit which is to be closed instantaneously and irreversibly. There terminals are disposed along the axis xx' of the box 13. They are, for example, made of copper and secured to the box by nuts 16a and 16b.

Each of the terminals 15a and 15b is rigid with a conductive plate 17a and 17b respectively. These plates are disposed perpendicular to the axis x-x'.

The plate 17a is rigid with a cylindrical electrode 18a and the plate 17b is rigid with a cylindrical external electrode 18b. The electrodes 18a and 18b are coaxial, metallic and separated by an intermediate space 190 which is very small, i.e. of the order of 1 mm. This space is filled with a first pyrotechnical composition 20 formed of a pulverulent mixture of a metallic oxide in which the metal is only slightly oxidized and easy to reduce, such as an oxide of lead, silver, copper or tin; and a metalloid reducer, for example, boron or silicon.

The plate 17b is also rigid with a metallic sleeve 21, for example, a sleeve of copper similar to the electrodes 18a and 18b. The sleeve is separated from the plate 17a by an insulative ring 22. The sleeve has an external diameter slightly less than the internal diameter of the electrode 18a such that it defines therewith a narrow intermediate space 19b of the order of 1 mm which is also filled with the first pyrotechnical composition 20.

The internal electrode 18a is therefore disposed between the electrode 19a and the sleeve 21 which are electrically connected by the conductive plate 17b and it is insulated from these on their two faces by the first pyrotechnical composition 20 which is electrically insulative.

As the relay is adapted to high power, the dielectric rigidity between the electrodes can be increased by applying on the faces thereof and on the periphery of the sleeve a layer of combustible varnish, such as nitrocellulose, which burns without producing solid residue under the effect of the increase of temperature due to the reaction of the pyrotechnical composition 20.

In order to effect the activation of the composition 20, the box 13 has a lateral orifice 23 in which is disposed an insulative plate 24 carrying on its internal face a bead 25 of the second pyrotechnical composition. A filament 26 is connected to two external terminals 27a and 27b which permit control of the initiation of the bead 25 by means of electrical signals of short duration.

For security purposes the relay can be provided with a second identical activation means. A thin coating of the second pyrotechnical composition can be disposed on the interior face of the box 13 in order to produce a rapid initiation of the first composition.

The electrodes 18a and 18b are provided with holes 28 in order to facilitate the energization of the first pyrotechnical composition 20.

The size of the relayjust described is several centimeters. As in the preceding case, an electrical signal, for example, an impulse of short duration sent from the circuit connected to the terminals 27a and 27b causes initiation of the composition 25 and thereby of the composition 20. This frees the metal from the oxide in composition 20 which results in welding of the two faces of the electrode 18a with the electrode 18b and the sleeve FIGS. 5-7 show another embodiment comprising a multiple relay adapted to be mounted in circuits under the same conditions as integrated circuits of analogous type. The relay is composed of a box 30 closed by a base plate 31. Two rows of conductive plates 32 and 33 are connected to external connections 32a and 33a, each row comprising, for example, eight connections forming four pairs.

The pairs of plates of the row 32 are connected to one another by a filament 34 covered by a layer of first pyrotechnical composition 35. The filaments 34 and the composition 35 are placed in cavities 36.

The pairs of plates of the row 33 are connected to pairs of concentric metallic electrodes 37a and 37b separated by a small space of the order of 0.5 mm which is filled with second pyrotechnical insulative composition 39.

An insulator 40, for example, a polymeric resin encapsulates the plates and the electrodes provided in the four cavities 36 and the four cavities which make communication between the cavities 36 and the extremity of the electrodes 37.

The pyrotechnical composition 39 is constituted, as previously, of a pulverulent mixture of a slightly oxidized metal selected from the group of lead, tin, silver and copper and a reductive metalloid of boron or silicon.

The operation is as follows:

A control signal is set which can be an impulse of small duration from a circuit connected to one of the pairs of connectors 32a. The filament 34 corresponding thereto is heated and melts initiating combustion of the pyrotechnical charge 35. This charge can be of any conventional type well kwown in the art. It produces the initiation of the first charge 39 corresponding thereto and the instantaneous decomposition reaction of the metallic oxide to liberate the metal which causes the welding of the two electrodes 37a and 37b and the irreversible closure of the corresponding electrical circuit.

The outside dimensions of the relay in FIGS. 5-7 are of the order of 1 cm.

The connections of such relay are identical to those of the flat boxes of integrated circuits such that it can be easily plugged into printed circuits as integrated circuits and they are interchangeable therewith.

FIG. 8 is a variant of FIG. 1 and shows in section a static relay of small size and low weight comprising a box 101 closed by a base member 102.

The interior of the box contains two main separate parts, namely cover 103 and support 104.

The support 104 is preferably made of an insulative resin of polyphenol sulfur (Ryton 4) which is an injection moulded product offering the advantage relatively of being inexpensive compared to ceramics while possessing sufficient resistance to heat released at the time of the reactions.

Two conductors 105 are mounted in the support 104 in symmetrical positions, with respect to the central axis of the box, at the time of moulding by two drops of solder, such that the extremities 106 of the conductors protrude just beyond the plane of separation of the support 104 and the cover 103. These extremities 106 are connected to an actuator filament 107, for example, of Tophet. In a preferential embodiment, the filament is electrically soldered to the extremities 106 of the conductors. The extremities 106 are then covered with an electrical insulator 108 preferably a drop of Araldite. This insulator covers the entire portion of the extremities projecting from the support 104.

The support 104 is provided with an annular groove coaxial with the box, adapted to receive two electrodes 109 and 110, preferably of nickel, the electrodes being in the shape of annular plates which are coaxial with respect to the box 101 and separated from one another.

This concentric form provides a maximum surface of contact after the initiation of the first pyrotechnical composition and providing high resistance to thermal actions, which are developed during the very exothermic reactions of the-pyrotechnical compositions utilized.

In the space between the two electrodes, there is dis posed an annular envelope 111 of channel crosssection which defines with electrode 109 a closed space containing the first pyrotechnical composition 112. The envelope 111 is separated from the other electrode 110 by a thin layer of air 113.

In the embodiment illustrated in FIG. 8, the envelope is preferably made of tin and has a thickness of 0.15 mm. The flanges of the envelope bear against the internal electrode 109 to define therewith the closed space containing the pyrotechnical composition 112. The envelope is so spaced from the electrical 110 that the layer of air has a thickness of 0.15 mm.

The presence of the envelope of tin assures electrical insulation between the electrodes and relieves the first composition of application of all electrical voltage while providing a high breakdown voltage. Furthermore, the insulating property of the first pyrotechnical composition as required in the previous embodiments before initiation of the first composition, is no longer required. Another advantage provided by the envelope is in the residual resistance. In a variant, the thickness of the envelope is increased and the size of the space for the first composition is reduced, as a function of the distance separating the web of the enveloping from the electrode 106 taking into account the minimum quantity of the first pyrotechnical composition which is necessary to effect fusion of the tin of the envelope.

The internal electrode 109 has orifices 115 therein, establishing communication between the first pyro technical composition and the second pyrotechnical composition 116 on the support 104 at the interior of the internal electrode 109. Between the cover 103 and the support 104, there is formed a cavity laterally bounded by the internal electrode 109. In this cavity project the extremities 106 of the conductors 105 which are covered by insulator 108 and connected by actuating filament 107. On the filament is a layer of the second composition 116 and the composition is maintained against said filament by a membrane 114.

In the embodiment illustrated in FIG. 8 according to a non-limiting example, the membrane 114 has the form of a paper disc of 4.5 mm diameter, with bent edges abutting against the internal face of the electrode 109 in order to maintain 3 mg. of the second composition 116 on the filament.

The membrane 114 defines with a cavity in the cover 103 a detent chamber 117, which serves to limit the internal pressure at the timeof the reaction of the utilized pyrotechnical compositions.

As before, the first pyrotechnical composition is preferably composed of an oxide of a heavy metal preferably only slightly oxidized and easily reduced, and a metalloid of low atomic weight which is a strong reducing agent. Preferably, a composition of silver oxide and boron is utilized.

As before, the second pyrotechnical composition 1 16 should release after initiation, a heat of combustion sufficient to initiate the first pyrotechnical composition with as little gas production as possible. Also it should have electrically insulative properties before and after combustion, as well as good burning properties. A preferably composition is a mixture which comprises 20% potassium chromate, 20% lead dioxide and 60% zironium.

The filament 107 is fed with an electrical actuating signal for several tens of milliseconds which causes the initiation of combustion of the second pyrotechnical composition. When sufficient heat has been released by this combustion, the first pyrotechnical composition is ignited.

Through the orifice 115 traversing the internal electrode 109, the combustion flames of the second composition initiate the reaction of the first composition, which in the preferred embodiment, is transformed into beads of silver. This reaction is very exothermic and causes melting of the tin envelope and its plating on the external electrode 110 under the pressure of the gas formed at the time of the reaction. The layer of air 113 disappears and the welding between the electrodes with the silver and the tin is effected, to assure the closure of the circuit at least 5 milliseconds after feed of the filament 107.

The relay box has its base welded electrically and contains the pressure of the gas formed during the reactions of the compositions.

FIGS. 9 and 10 show a further embodiment similar to FIGS. 5-7 applicable in the case where a group of relays of identical construction are utilized in electrical circuits of low power or in logical circuits requiring closure a single time.

Therein a box 121 is closed by a base 122 and comprises two rows of conductive plates 123 and 124. Each plate 123 corresponds either to a central electrode 125 or an annular coaxial electrode 126 which form a common assembly separated by a space containing a first composition 127 encased by a hollow envelope 128 having a flange bearing against electrode 127 and separated from the other electrode 125 by a thin layer of air 129.

Each plate 124 corresponds to a conductor connected in the actuator circuit. The conductors are connected two-by-two at their extremities to a filament 131, covered by second pyrotechnical composition 132, which is compressed against the filament by a membrane 133 having bent edges forming a detent chamber 134 for expansion of the gas formed at the time of combustion of the second composition 132. The chamber 134 communicates with a space in turn communicating with the first pyrotechnical composition 127 to permit the initiation of the latter, at the time of combustion of the second composition.

The extremities of the conductors are coated with an insulator resistant to the heat released by the reactions of the compositions and assuring the electrical isolation of these extremities with the second pyrotechnical composition.

A control signal of short duration sent to one pair of two plates 124 effects energization of the filament 131 therebetween which produces combustion of the second composition 132 causing the irreversible closure of the circuit between the corresponding pair of two plates 123 by combustion of the first pyrotechnical composition.

FIG. 1 1 is similar to FIG. 3 and is a transverse section of an embodiment of a relay for high current intensities greater than 100 amp.

In FIG. ll is seen an insulative cylindrical box 141 closed by a threaded stopper 142 and comprising two connection terminals 143 and 144 disposed along the axis xx.

Each terminal 143, 144 is attached to a conductive plate 145, 146 respectively, these being disposed perpendicularly to the axis xx' and facing one another.

The plate 145 is prolonged by an internal annular electrode 147.

The plate 146 is prolonged by an external annular electrode 148.

The plate 146 is also rigid with a metallic sleeve 150 coaxial with and separated from the plate 145 by an insulator and separated from the internal electrode 147 by a space enclosing successively from said sleeve to said electrode;

a thin layer of air 160,

an annular envelope 153 having bent edges bearing against the internal electrode 147 and defining therewith a closed space; and

the first composition 151 in said closed space.

The electrodes 147 and 148 are separated by a space successively enclosing between the electrode 147 and the electrode 148;

a thin layer of air 161;

an annular envelope 152 having two bent edges and defining with the external electrode 148 a closed space; and

the first composition 151 in said closed space.

Externally and laterally of the electrode 148 is a detent chamber 156 which is annular for attenuating the effect of the gas produced in the course of combustion of the second pyrotechnical composition.

The actuation is effected by plug 157 placed in lateral orifice 158 in a manner to feed a filament and permit the combustion of the second composition 149 disposed in an annulus around the electrode 147 in which are provided orifices 155 which permit the initiation of the reaction of the first composition 151.

In the same manner, the reaction of the first composition 151 is initiated by the orifices 154 traversing the external electrode 148.

What is claimed is:

l. A static relay comprising two spaced metallic electrodes which are electrically isolated from one another, a coating of a layer of tin on said electrodes, a first py rotechnical composition disposed between said electrodes, a second pyrotechnical composition separated from the first pyrotechnical composition, means for initiating combustion of the second pyrotechnical composition by application of an electrical signal, said first composition being so disposed with respect to the second composition to be initiated by the reaction thereof, said first composition being so constituted as to form a conductive body, under the heat released by the reaction of the first composition, which effects welding of the metallic electrodes together.

2. A relay as claimed in claim 1 wherein said first pyrotechnical composition comprises a pulverulent mixture of a metal oxide and a metalloid reducer, said pulverulent mixture being compressed between said electrodes and further containing oil of methyl silicone.

3. A relay as claimed in claim 2 wherein said metal oxide has a voltage for oxygen reduction of at least O. 15 volts.

4. A relay as claimed in claim 3 wherein said metal oxide is an oxide of a metal selected from the group consisting of tin, lead, copper, and silver and said metalloid is boron or silicon.

5. A relay as claimed in claim 2 wherein said conductive body is formed by the reduction of the metal oxide which yields molten metal serving to weld the electrodes together.

6. A relay as claimed in claim 1 comprising a coating of an insulative varnish on said electrodes, said varnish burning at the temperature of combustion of said first composition without forming solid residues.

7. A relay as claimed in claim 1 wherein said electrodes comprises parallel plates with a spacing therebetween filled with said first composition, the latter being electrically insulative.

8. A relay as claimed in claim 7 wherein said plates are cylindrical and coaxial, one electrode being internal, the other external.

9. A relay as claimed in claim 8 comprising a sealed box enclosing said electrodes, conductors connected to a respective electrode and extending externally of said box, insulator means in said box mounting said electrodes and conductors therein and defining a cavity in the interior of the internal electrode, said second compostion being disposed in said cavity, said means for initiating combustion of said second composition comprising a filament which is electrically energized and is in Contact with said second composition, said internal electrode being provided with holes establishing communication between said cavity and the spacing between the electrodes.

10. A relay as claimed in claim 9 wherein said means for initiating combustion of said second composition further comprises further conductors connected to said filaments and extending externally of the box for the application of an electrical activating signal thereto.

11. A relay as claimed in claim 8 comprising an insulative box enclosing said electrodes, a metallic conductive sleeve electrically connected to the external electrode and disposed within the internal electrode with a space therebctween, said first composition filling the later space, two conductors, each connected to a respective electrode, said box having a lateral opening, said means for initiating combustion of the second composition comprising an insulative plate mountable in said orifice in the box, said plate having an internal face on which said second composition is mounted, and further conductors mounted on said plate in contact with the second composition and extending externally of said plate.

12. A relay as claimed in claim 11 wherein said box is cylindrical, said conductors which are connected to said electrodes being mounted in alignment on said box along the axis thereof, and conductive plates mounted in said box and providing electrical connection between a respective electrode and conductor.

13. A plurality of relays as claimed in claim 8 comprising a flat box enclosing the relays, two rows of connectors extending from said box and projecting thereinto, means for initiating combustion of said second composition, filaments connecting the connectors of one row, two-by-two, one pair for each relay, each said filament being embedded in said second pyrotechnical composition, the connectors of the other row being connected in pairs to respective electrodes of each relay.

14. A static relay comprising two spaced metallic electrodes which are electrically isolated from one another, a first pyrotechnical composition disposed between said electrodes, a second pyrotechnical composition separated from the first pyrotechnical composition, means for initiating combustion of the second pyrotechnical composition by application of an electrical signal, said first composition being so disposed with respect to the second composition to be initiated by the reaction thereof, said first composition being so constituted as to form a conductive body, under the heat released by the reaction of the first composition, which effects welding of the metallic electrodes together, means defining a layer of air between said first pyrotechnical composition and said electrodesto electrically insulate said electrodes, said layer of air disappearing under the effect of combustion of the first composition.

15. A relay as claimed in claim 14 wherein said means which defines said layer of air comprises an envelope between said electrodes defining with one of said electrodes a chamber containing said first composition, said envelope being spaced from the other electrode to define therewith said layer of air.

16. A relay as claimed in claim 15 wherein said envelope is constituted of a combustible material.

17. A relay as claimed in claim 15 wherein said electrodes are cylindrical and coaxial, said envelope comprising a ring coaxial with said electrodes and including at least one flange defining said chamber with said one electrode.

18. A relay as claimed in claim 15 wherein said electrodes are welded under the effect of the heat released by combustion of the second composition, said envelope being constituted of a conductive metal which melts and combines with said conductive body to effect welding of the electrodes. I

19. A relay as claimed in claim 14 wherein said means for initiating combustion of said second composition comprises two conductors having extremities, a filament connected to said extremities and in contact with said second composition, and a coating on said extremities covering the same and the connection of the filament therewith, said coating being constituted of a material which is electrically insulative and resistant to the heat released by the combustion of the second pyrotechnical composition.

20. A relay as claimed in claim 19 comprising a membrane applied against said second composition on the face thereof remote from that in contact with said filament to maintain said second composition thereagainst.

21. A relay as claimed in claim 14 comprising a sealed box enclosing said electrodes, said electrodes being cylindrical and coaxial, one electrode being internal, the other external, conductors connected to a respective electrode and extending externally of said box, insulator means in said box mounting said electrodes and conductors therein and defining a cavity in the interior of'the internal electrode, said second composition being disposed in said cavity, said means for initiating combustion of said second composition comprising a filament which is electrically energized and is in contact with said second composition, said internal electrode being provided with holes establishing communication between said cavity and the spacing between the electrodes, said means defining said layer of air comprising a ring member in the space between the electrodes defining with one of said electrodes a closed chamber containing the first pyrotechnical composition, said ring member defining with the other electrode said layer of air.

22. A relay as claimed in claim 21 wherein said means for initiating combustion of said second composition further comprises further conductors connected to said filament and extending externally of the box for the application of an electrical activating signal thereto.

23. A relay as claimed in claim 22 wherein said further conductors have extremities to which said filament is attached, and a coating on said extremities covering the same and the connection of the filament therewith, said coating being constituted of a material which is electrically insulative and resistant to the heat released by the combustion of the second pyrotechnical composition.

24. A relay as claimed in claim 23 wherein said box is of insulative material and comprising a metallic conductive sleeve electrically connected to the external electrode and disposed within the internal electrode with a space therebetween, said first pyrotechnical substance filling said space, said box having a lateral open ing in which is engageable said means for initiating combustion of the second composition.

25. A plurality of relays as claimed in claim 20 comprising a fiat box enclosing the relays, two rows of connectors extending from said box and projecting thereinto, said filaments connecting the connectors of one row, two-by-two, one pair for each relay, each said filament being embedded in said second pyrotechnical composition, the connectors of the other row being connected in pairs to respective electrodes of each relay.

26. A plurality of relays as claimed in claim 25 wherein said electrodes of eachrelay are coaxial cylinders between which is said layer of air which is annular and said first pyrotechnical composition, an insulator filling said box and providing two cavities therein which communicate with one another, said second composition being in part of one cavity and the first composition in part of the other cavity, said means defining said layer of air comprising a ring arranged between said electrodes and defining with one electrode a closed chamber containing the first pyrotechnical composition, said ring defining with the other electrode said layer of air. 

1. A static relay comprising two spaced metallic electrodes which are electrically isolated from one another, a coating of a layer of tin on said electrodes, a first pyrotechnical composition disposed between said electrodes, a second pyrotechnical composition separated from the first pyrotechnical composition, means for initiating combustion of the second pyrotechnical composition by application of an electrical signal, said first composition being so disposed with respect to the second composition to be initiated by the reaction thereof, said first composition being so constituted as to form a conductive body, under the heat released by the reaction of the first composition, which effects welding of the metallic electrodes together.
 2. A relay as claimed in claim 1 wherein said first pyrotechnical composition comprises a pulverulent mixture of a metal oxide and a metalloid reducer, said pulverulent mixture being compressed between said electrodes and further containing oil of methyl silicone.
 3. A relay as claimed in claim 2 wherein said metal oxide has a voltage for oxygen reduction of at least - 0.15 volts.
 4. A relay as claimed in claim 3 wherein said metal oxide is an oxide of a metal selected from the group consisting of tin, lead, copper, and silver and said metalloid is boron or silicon.
 5. A relay as claimed in claim 2 wherein said conductive body is formed by the reduction of the metal oxide which yields molten metal serving to weld the electrodes together.
 6. A relay as claimed in claim 1 comprising a coating of an insulative varnish on said electrodes, said varnish burning at the temperature of combustion of said first composition without forming solid residues.
 7. A relay as claimed in claim 1 wherein said electrodes comprises parallel plates with a spacing therebetween filled with said first composition, the latter being electrically insulative.
 8. A relay as claimed in claim 7 wherein said plates are cylindrical and coaxial, one electrode being internal, the other external.
 9. A relay as claimed in claim 8 comprising a sealed box eNclosing said electrodes, conductors connected to a respective electrode and extending externally of said box, insulator means in said box mounting said electrodes and conductors therein and defining a cavity in the interior of the internal electrode, said second compostion being disposed in said cavity, said means for initiating combustion of said second composition comprising a filament which is electrically energized and is in contact with said second composition, said internal electrode being provided with holes establishing communication between said cavity and the spacing between the electrodes.
 10. A relay as claimed in claim 9 wherein said means for initiating combustion of said second composition further comprises further conductors connected to said filaments and extending externally of the box for the application of an electrical activating signal thereto.
 11. A relay as claimed in claim 8 comprising an insulative box enclosing said electrodes, a metallic conductive sleeve electrically connected to the external electrode and disposed within the internal electrode with a space therebetween, said first composition filling the later space, two conductors, each connected to a respective electrode, said box having a lateral opening, said means for initiating combustion of the second composition comprising an insulative plate mountable in said orifice in the box, said plate having an internal face on which said second composition is mounted, and further conductors mounted on said plate in contact with the second composition and extending externally of said plate.
 12. A relay as claimed in claim 11 wherein said box is cylindrical, said conductors which are connected to said electrodes being mounted in alignment on said box along the axis thereof, and conductive plates mounted in said box and providing electrical connection between a respective electrode and conductor.
 13. A plurality of relays as claimed in claim 8 comprising a flat box enclosing the relays, two rows of connectors extending from said box and projecting thereinto, means for initiating combustion of said second composition, filaments connecting the connectors of one row, two-by-two, one pair for each relay, each said filament being embedded in said second pyrotechnical composition, the connectors of the other row being connected in pairs to respective electrodes of each relay.
 14. A static relay comprising two spaced metallic electrodes which are electrically isolated from one another, a first pyrotechnical composition disposed between said electrodes, a second pyrotechnical composition separated from the first pyrotechnical composition, means for initiating combustion of the second pyrotechnical composition by application of an electrical signal, said first composition being so disposed with respect to the second composition to be initiated by the reaction thereof, said first composition being so constituted as to form a conductive body, under the heat released by the reaction of the first composition, which effects welding of the metallic electrodes together, means defining a layer of air between said first pyrotechnical composition and said electrodes to electrically insulate said electrodes, said layer of air disappearing under the effect of combustion of the first composition.
 15. A relay as claimed in claim 14 wherein said means which defines said layer of air comprises an envelope between said electrodes defining with one of said electrodes a chamber containing said first composition, said envelope being spaced from the other electrode to define therewith said layer of air.
 16. A relay as claimed in claim 15 wherein said envelope is constituted of a combustible material.
 17. A relay as claimed in claim 15 wherein said electrodes are cylindrical and coaxial, said envelope comprising a ring coaxial with said electrodes and including at least one flange defining said chamber with said one electrode.
 18. A relay as claimed in claim 15 wherein said electrodes are welded under tHe effect of the heat released by combustion of the second composition, said envelope being constituted of a conductive metal which melts and combines with said conductive body to effect welding of the electrodes.
 19. A relay as claimed in claim 14 wherein said means for initiating combustion of said second composition comprises two conductors having extremities, a filament connected to said extremities and in contact with said second composition, and a coating on said extremities covering the same and the connection of the filament therewith, said coating being constituted of a material which is electrically insulative and resistant to the heat released by the combustion of the second pyrotechnical composition.
 20. A relay as claimed in claim 19 comprising a membrane applied against said second composition on the face thereof remote from that in contact with said filament to maintain said second composition thereagainst.
 21. A relay as claimed in claim 14 comprising a sealed box enclosing said electrodes, said electrodes being cylindrical and coaxial, one electrode being internal, the other external, conductors connected to a respective electrode and extending externally of said box, insulator means in said box mounting said electrodes and conductors therein and defining a cavity in the interior of the internal electrode, said second composition being disposed in said cavity, said means for initiating combustion of said second composition comprising a filament which is electrically energized and is in contact with said second composition, said internal electrode being provided with holes establishing communication between said cavity and the spacing between the electrodes, said means defining said layer of air comprising a ring member in the space between the electrodes defining with one of said electrodes a closed chamber containing the first pyrotechnical composition, said ring member defining with the other electrode said layer of air.
 22. A relay as claimed in claim 21 wherein said means for initiating combustion of said second composition further comprises further conductors connected to said filament and extending externally of the box for the application of an electrical activating signal thereto.
 23. A relay as claimed in claim 22 wherein said further conductors have extremities to which said filament is attached, and a coating on said extremities covering the same and the connection of the filament therewith, said coating being constituted of a material which is electrically insulative and resistant to the heat released by the combustion of the second pyrotechnical composition.
 24. A relay as claimed in claim 23 wherein said box is of insulative material and comprising a metallic conductive sleeve electrically connected to the external electrode and disposed within the internal electrode with a space therebetween, said first pyrotechnical substance filling said space, said box having a lateral opening in which is engageable said means for initiating combustion of the second composition.
 25. A plurality of relays as claimed in claim 20 comprising a flat box enclosing the relays, two rows of connectors extending from said box and projecting thereinto, said filaments connecting the connectors of one row, two-by-two, one pair for each relay, each said filament being embedded in said second pyrotechnical composition, the connectors of the other row being connected in pairs to respective electrodes of each relay.
 26. A plurality of relays as claimed in claim 25 wherein said electrodes of each relay are coaxial cylinders between which is said layer of air which is annular and said first pyrotechnical composition, an insulator filling said box and providing two cavities therein which communicate with one another, said second composition being in part of one cavity and the first composition in part of the other cavity, said means defining said layer of air comprising a ring arranged between said electrodes and defining with one electrode a closed chamber coNtaining the first pyrotechnical composition, said ring defining with the other electrode said layer of air. 